It is often desirable and frequently necessary to sample or test a portion of tissue from humans and other animals, particularly in the diagnosis and treatment of patients with cancerous tumors, pre-malignant conditions, and other diseases and disorders. Typically, in the case of cancer, when the physician establishes by means of procedures such as palpation, x-ray, or ultrasound imaging that suspicious circumstances exist, a biopsy is performed to determine whether the cells are cancerous. Biopsy may be done by an open or percutaneous technique. Open biopsy, which is an invasive surgical procedure using a scalpel and involving direct vision of the target area, removes the entire mass (excisional biopsy) or a part of the mass (incisional biopsy). Percutaneous biopsy, on the other hand is usually done with a needle-like instrument through a relatively small incision, blindly or with the aid of an artificial imaging device, and may be either a fine needle aspiration (FNA) or a core biopsy. In FNA biopsy, individual cells or clusters of cells are obtained for cytologic examination and may be prepared such as in a Papanicolaou smear. In core biopsy, as the term suggests, a core or fragment of tissue is obtained for histologic examination which may be done via a frozen section or paraffin section.
The type of biopsy utilized depends in large part on circumstances present with respect to the patient, and no single procedure is ideal for all cases. However, core biopsy is extremely useful in a number of conditions and is being used more frequently by the medical profession.
One particular type of image guided percutaneous core breast biopsy instrument currently available is a vacuum-assisted automatic core biopsy device. One such successful biopsy device is shown and disclosed in U.S. Pat. No. 5,526,822, to Burbank et al., which is expressly incorporated by reference herein, and in the previously referenced related patent application Ser. No. 08/386,941, both of which are commonly owned by the assignee of the present application, and is presently commercially available under the trademark MAMMOTOME. This device includes a piercing cannula and a cutting cannula and has the capability to actively capture tissue prior to cutting the tissue, meaning that vacuum pressure is used to "draw" the tissue into a capture notch. Mechanisms are included for rotationally orienting the piercing cannula, which has a tissue capture notch near the distal end thereof, so that the notch is in a desired angular orientation for receiving a tissue sample. Additional mechanisms permit the cutting cannula to travel axially, so that it may be retracted and advanced as desired and rotationally, in order to assist the cutting process. Active capture allows for sampling through non-homogeneous tissues, meaning that the device is equally capable of cutting through hard and soft tissue. The device also includes means to direct and position the cutting chamber in arbitrary positions about and along its longitudinal axis, means for rapid and atraumatic removal of an arbitrary number of core samples with only a single insertion into the body and organ, and means for coding and decoding the location from which the samples were obtained. Together, these capabilities allow for more complete sampling of large lesions and for the complete removal of small lesions. This type of instrument is advantageous in that it permits the obtainment of a plurality of tissue samples from different locations with only a single instrument insertion. Consequently, a wide area of tissue within the body may be excised through a single small opening, so as to greatly reduce resultant trauma to the patient. Use of this kind of instrument also produces high quality samples in a manner which does not require direct handling of the samples by the operator.
Presently, vacuum-assist automatic core biopsy devices of the type disclosed in the aforementioned '822 patent have been manually operated once the piercing cannula of the device is located as desired adjacent to a target lesion. In particular, vacuum pressure has typically been applied simultaneously to both the vacuum and cutter lumens during a procedure by manually operating a source of vacuum pressure when a region of vacuum adjacent to the tissue receiving notch is desired It would thus be a significant advantage to be able to automatically control the application of vacuum pressure during the procedure, so that the user is free to entirely concentrate on the medical procedure itself and in order to enhance the accuracy and efficiency of the procedure.
It has been found through usage of vacuum-assist automatic core biopsy devices of this type that vacuum management techniques are valuable not only for drawing tissue into the capture notch, but also to assist in transport of the tissue specimen proximally through the instrument and out of the patient's body. To elaborate, because of differential pressures developed within the biopsy probe during the course of the procedure, efficient transport of the tissue specimen outside of the body does not always occur. For example, sometimes as the cutter is retracted, the specimen remains at the distal section of the probe and thus inside the body. If pressure at the proximal end of the specimen can be established that is lower than the pressure at the distal end of the specimen, a favorable pressure differential will exist which will improve the likelihood that the tissue specimen will travel proximally with the cutter to the designated tissue receptacle.
During a tissue specimen removal procedure, a significant quantity of blood and small excess tissue pieces are generated by the cutting process. Presently, this blood and tissue is drawn back through the cutter lumen when vacuum is applied thereto to assist in retrieving the tissue specimen, and exits from the proximal end of the device in the vicinity of the tissue specimen receptacle. This is a problem in that it obscures the practitioner's view of the specimen as it is being retrieved, and additionally complicates the objective of obtaining an intact specimen. It would therefore be a further advantage to be able to operate the vacuum system so that such blood and tissue is effectively removed to a site remote from that of the tissue specimen receptacle, and in such a manner that it does not interfere with the effective obtainment of intact specimens. Furthermore, it would be yet another advantage to be able to selectively apply differential vacuum pressure throughout the probe, automatically, in order to in order to assist in the removal of clogging debris from the various lumens and ports.